[Quoth]

No B&W eink would lead ultimately to the demise of eink. Kaleido is worse than matt screen LCD/OLED because it needs a bright frontlight and there are phones & tablets with matt screens and now good enough run time. Also the resolution/sharpness and contrast of Kaleido color is worse than any 300 dpi Carta eink and decent matt screen LCD/OLED.

Gallery is not as dark and better colour but abysmally slow. The regular eink is already slow and Gallery is x10 slower.

The Kaleido screens can't really improve as it's coloured dots on a Carta1300. There is no sign of Carta getting more than 300 dpi mono (11 years ago, 2014). Even if it was higher resolution, Kaleido is inherently dark.

Kaleido is 6 years old and could have been done in 2005 (First Sony eink) as it's simply a 2 x 2 array of dots that don't completely cover the Carta mono eink screens, which still only have 14 levels with black and white since 2013, same as 2010 Pearl.

The variations of Carta since 300 dpi and variations of Kaleido have been minor tweaks.

The Gallery system is a different principle of panel with inherent Cyan, Yellow and Magenta added to the white. The Advanced Color ePaper (ACeP) or Gallery is from 2016, a 9 year old system with subsequent tweaks. It's for shop displays and poor competition for video panels. About 65K colours/shades.

I've seen Kaleido 3 first hand and it's like 2006-2007 eink, though with more shades (4096 inc white, black and greys). Abysmal. Unusable indoors without a front light. The 300 dpi mono mode is inferior to mono panels and has artefacts. It's only artefact free at 150 dpi (the colour resolution), which was only on the 9.7" Viziplex (DX) and Pearl (DXG) panels.

Colour eink adverts are almost all misleading.

EDIT:
Really Kindle Voyage in 2014, 11 years ago was "peak" eink based ereader. There have only been incremental eink panel improvements – increased size, printed colour overlays for colour and stylus/digitisers – since. Only the larger sizes are actual eink advances (ACeP isn't the same system and wasn't intended for ereaders).

And the majority of ebooks are now read on phones and tablets, which were not anything like as good in 2005 or even 2014 for battery life or screen quality.